It is common practice in the use of threaded mechanical fasteners such as nut/bolt assemblies, to apply to one or more of the threadable engagement surfaces thereof, an adhesive/sealant composition termed a threadlocking composition, for the purpose of locking and/or sealing the constituent members of such fasteners when they are threadingly engaged.
Threadlocking compositions known in the art include co-reactive adhesive systems. With this type of threadlocking system, two or more components are mixed before applying the resulting composition to the threaded engagement surface(s) of the fastener on which the components in the threadlocking composition react to cure. Examples of such co-reactive systems include epoxy resin adhesive compositions.
Liquid adhesive compositions have long been used in sealing and threadlocking applications and have become a standard part of assembly production as well as in the maintenance of machinery, tools and the like. Among the liquid adhesive compositions commonly used in these applications are anaerobic compositions. These single part compositions provide excellent threadlocking and sealant properties and remain stable until they are placed between parts where they cure in the absence of air. Moreover, these compositions remain stable for long periods of time during storage in the bottle.
There are several other disadvantages associated with the use of conventional liquid anaerobic threadlockers, as well as prior non-flowable, thixotropic anaerobic-based threadlockers. One additional disadvantage is the inability of such compositions to cure through large gaps. Another disadvantage is that due to their anaerobic nature, portions of the adhesive which remain exposed to air once applied to the parts will not cure. For example, external bondlines which remain exposed to air on a nut and bolt assembly will remain liquid unless additional additives and cure measures are taken to ensure cure. As a result, liquid compositions at the external bondlines may tend to migrate. In the case of conventional non-flowable compositions, which depend on the thixotropic and/or rheological properties of the composition for their non-flowability, these compositions will flow if the temperature is high enough. Additionally, uncured materials may be easily extracted from such compositions by interaction with the environment. Such leaching of components from the compositions can create contamination problems and hazardous conditions for the surroundings.
It would be extremely useful and a significant advance in the field of reactive threadlockers and sealants, to provide a surface-independent reactive composition particularly useful for threadlocking applications, which overcomes the disadvantages of the prior art compositions. There is a need also for overcoming the disadvantages attendant the prior threadlocking compositions while providing a cost effective, dry-to-the-touch, easy to apply composition.